1. Field of the Invention
The present invention relates generally to magneto-resistive (MR) stripe elements for use in magnetic read heads and, more particularly, to an MR stripe element having a thin film electrical conductor covered by an electrically conductive capping layer which form a combined structure having a minimized compressive stress.
2. Background Art
Magnetic read heads include magneto-resistive (MR) stripe elements for reading data from a storage medium such as tape. In general, MR stripe elements sense magnetic flux from a magnetic storage medium to read data stored on the magnetic storage medium. MR stripe elements incur a change in resistivity in the presence of a magnetic field. A typical magnetically active MR material used for an MR stripe element is the alloy of nickel (Ni) and iron (Fe) with a 4:1 Nixe2x80x94Fe ratio, i.e., permalloy.
In one embodiment, the entire area of an MR stripe element is entirely composed of an Nixe2x80x94Fe film material. A problem with the entire area of an MR stripe element being entirely composed of an Nixe2x80x94Fe film material is that Nixe2x80x94Fe film material is present in inactive areas of the MR stripe element. A further problem with the entire area of an MR stripe element being entirely composed of an Nixe2x80x94Fe film material is that Nixe2x80x94Fe film material present in active areas influences the passive resistance, magnetic track width, Barkhausen noise, and other important read head performance properties.
Accordingly, an improved MR stripe element design has the Nixe2x80x94Fe film material in the inactive areas removed. The improved MR stripe element further replaces the Nixe2x80x94Fe film material present in the active areas with a thin film electrical conductor. In such case, the thin film conductor defines the magnetic track width and reduces the passive resistance. A relatively small number of thin film electrical conductor materials are suitable for exposure between the read head/tape interface. Such factors for determining which thin film electrical conductor materials are suitable include resistivity, wear, corrosion, stress/delamination, and cost. For example, thin film electrical conductor materials such as copper and gold are not suitable because they are soft and have a tendency to smear. Other thin film electrical conductor materials such as rhodium are prohibitively expensive.
A thin film electrical conductor material which does meet the suitability factors is alpha-tantalum (alpha-Ta). Alpha-Ta is a low resistivity phase of Ta formed by a structure having a chromium (Cr) base layer formed adjacent to a Ta layer. An alpha-Ta thin film conductor is a bi-layer structure having two distinct layers (a Cr base layer and a Ta layer) and is not a mixture. During fabrication of an MR stripe element, the Cr base layer is deposited prior to deposition of the Ta layer. Subsequently, the Ta layer is deposited on the Cr base layer. The Cr base layer influences the micro-structure of the subsequently deposited Ta layer.
It has been demonstrated that the alpha-Ta (Cr/Ta) bi-layer thin film conductor has a desired resistivity when the two layers are deposited by using ion beam deposition. However, it has also been demonstrated that the compressive stress of the alpha-Ta bi-layer thin film conductor after deposition is relatively high. Because of the high compressive stress, there are concerns with respect to the ability of the alpha-Ta bi-layer thin film conductor to adhere to the rest of the film stack of an MR stripe element. It has been further demonstrated that the compressive stress of the alpha-Ta bi-layer thin film conductor increases when exposed to a subsequent anneal which simulates the further processing steps that a read head having an MR stripe element may experience during fabrication.
In contrast to the demonstrations, it would be desirable if the compressive stress of the alpha-Ta bi-layer thin film conductor were effectively lowered after deposition of the two layers (Cr/Ta) as well as after exposure to an annealing.
Accordingly, it is an object of the present invention to provide a magneto-resistive (MR) stripe element having a thin film electrical conductor covered by an electrically conductive capping layer in order to form a combined structure having a minimized compressive stress.
It is another object of the present invention to provide an MR stripe element having inactive areas of an Nixe2x80x94Fe magnetic film material removed and active areas of the Nixe2x80x94Fe magnetic film material replaced with a combined structure formed by a thin film electrical conductor covered by an electrically conductive capping layer.
It is a further object of the present invention to provide an MR stripe element having an alpha-tantalum (chromium/tantalum; Cr/Ta) bi-layer thin film covered by an electrically conductive capping layer in order to form a combined alpha-Ta/capping tri-layer structure having a minimized compressive stress.
It is still another object of the present invention to provide an MR stripe element having an alpha-Ta bi-layer thin film covered by a Cr capping layer in order to form a combined alpha-Ta/Cr tri-layer structure having a minimized compressive stress.
It is still a further object of the present invention to provide an MR stripe element having an alpha-Ta bi-layer thin film covered by a Cr capping layer having a thickness dependent upon at least the thickness of the Cr base layer of the alpha-Ta bi-layer thin film in order to form a combined alpha-Ta/Cr tri-layer structure having a minimized compressive stress.
It is still yet another object of the present invention to provide an MR stripe element having an alpha-Ta bi-layer thin film covered by a Cr capping layer in order to form a combined alpha-Ta/Cr tri-layer structure having a minimized compressive stress after deposition of the alpha-Ta bi-layer thin film and the Cr capping layer.
It is still yet a further object of the present invention to provide an MR stripe element having an alpha-Ta bi-layer thin film covered by a Cr capping layer in order to form a combined alpha-Ta/Cr tri-layer structure having a minimized compressive stress after the combined structure undergoes annealing.
In carrying out the above objects and other objects, the present invention provides a magneto-resistive (MR) stripe element and a read head having the MR stripe element. The MR stripe element includes a magnetically active body portion and an electrical conductor structure arranged proximate the magnetically active body portion. The electrical conductor structure includes an alpha-Ta bi-layer film and an electrically conductive capping layer. The alpha-Ta bi-layer film includes a chromium base layer and a tantalum body layer. The electrically conductive capping layer caps the alpha-Ta bi-layer film such that the tantalum body layer is disposed between the chromium base layer and the electrically conductive capping layer.
The electrically conducting capping layer may be a chromium capping layer, a titanium capping layer, or a tungsten capping layer. The chromium base layer has a minimum thickness. The electrically conductive capping layer has a thickness dependent upon at least the thickness of the chromium base layer.
Further, in carrying out the above objects and other objects, the present invention provides a method of fabricating the MR stripe element. The method includes depositing an alpha-Ta bi-layer film proximate a magnetically active body portion by initially depositing a chromium base layer and then depositing a tantalum body layer on the chromium base layer. The method further includes depositing an electrically conductive capping layer on the alpha-Ta bi-layer film to cap the alpha-Ta bi-layer film such that the tantalum body layer is disposed between the chromium base layer and the electrically conductive capping layer. Preferably, the electrically conductive capping layer is a chromium capping layer. Preferably, the depositing steps include using ion beam deposition or sputtering.
Also, in carrying out the above objects and other objects, the present invention provides an MR stripe element having a magnetically active body portion and an electrical conductor structure arranged proximate the magnetically active body portion. The electrical conductor structure has a body capped by a capping layer. The capping layer has a lower compressive stress than the body such that the electrical conductor structure has a lower compressive stress than the compressive stress of the body.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description when taken in connection with the accompanying drawings.